Power tool



Oct. 21, 1941. c. F'. WARREN ETAL 2,260,268

POWER TOOL Filedmaroh 1, 1939 2 sheets-sheet 1 Oct. 2 1, 1941. c. F. WARREN Erm. 2,250,268

POWER ToorJ Filed March 1, 1959 2 sheets-sheet 2 mlllllll lullmml!! gawglmrre/w 2 Patented Oct. 21, 1941 POWER TOOL charles r. wanen ma william n. smith, Wynne, Ark., signora to The S a W Hydraulic Tool Compllyu Wynne Arkansas Ark., a Acox-poration of JUN l 6 1942 Application March l, 1939, Serial No. 259,291

15 Claims.

This invention relates to improvements in power tools and one of its A foremost purposes is to l provide atool for diversiiled uses, capable of delivering any degree of blows from the lightest to the heaviestwithin the power of the prime mover. An outstanding characteristic lof the tool is the utilization of a liquid column as the force transmitting means, this particular provision avoiding the danger to personal safety which occurs in the event of a blowout in a power tool wherein compressed air or a similar fluid immediately constitutes the source of power.

With respect to the latter statement, pneumatic hammers, drills, tampers and the like are mechanical elements of common knowledge. ,Tools of this kind are inodinately heavy in the majority of instances and always require anair compressor unit consisting of an internal combustion motor and a compressor engine.' 'Ihese factors are brought to attentionv toy emphasize the point that prevailing power tool equipment is not only heavy and cumbersome, but obviously expensive because of the accessories that are re' quired.

Instances have been known wherein pneumatic one being struck by a fragment of metal or being struck by the recoil of the hose. With this preamble in mind the objects of theinvention are as follows:

First, to provide a power 'tool which is fundaf mentally safe because of the avoidance of the use of a pressure medium such as compressed air, the latter being substituted by a liquid column which is the intermediary between the .impulse member and the hammer, said column being devoid of inherent pressure and thereforenot which includes a 'recoil chamber somewhere in the liquid conduit, capable rst of yielding in the event of a jamming of the hammer, thereby to (Cl. 12S-32) pressure, second, of beig adjustable to vary the initial static pressure on the hydraulic colu'mn and so enable the grading of the hammer blows from zero to the heaviest capable of delivery by 5 the prime mover.

Fourth, to provide a power appliance which has for its fundamental characteristic the confinement of a column of liquid in a conduit stopped up at its ends by closures which, although i0 necessarily movable are backed up from the outside by springs of sufficient tension to prevent them from ever departing from the ends of the liquid column thus eliminating the chance of ever forming a vacuum and, what is of most importance, consolidating and maintaining the liquid column and its working parts into an aptly entitled mass-unit, the solidarity of said column also depending upon a locked pressure device branching off from and in communication with the column.

Fifth, to provide a power tool of the character described which is fundamentally simple, thereby to make it available to a large number of potential users who are at present prevented from having the advantages of such a power tool because of the prevailing high cost.

Other objects and advantages will appear in the following speciilcation, reference being had to the accompanying drawings, in which: l

-30 Figure l is a partially elevational and sectional view of the power unit of the tool. v

Figure 2 is a longitudinal section of the hand implement which is operable by the power unit. Figure 3 is a detail view 'partially in-elevation -35 and section of the reciprocable hammer.

Figure 4 is a partially elevational and section-al view of the impulse member of the power uni Fig-ure 5 is a cross section taken on the. line Figure 6 is a sectional view of the impact piston of Fig. 4.

Figure 7 is a partially elevational and sec- 4 tional view of the recoil chamber.

of a power unit, generally designated I, and a. hand implement generally designated 2. The

1 power unit as its name might imply, is adapted to be located at some stationary place, that is to 50 say, the workman is free from it precisely as the workman who operates the known type 'of pneumatic hammer is free from the compressor unit that furnishes the power. The instant power unit I maybe and usually is so arranged that avoid a rupture of the hose by an excess of back .55 it -is readily transported from point to point.

In carrying out the invention provision is made n The hand implement 2, as its name implies.' is wielded by the operator, the unit I and implement 2 being connected by a -hose 3, this completing what has herein been termed the power tool.

Notwithstanding the fact that the power unit and the hand implement are located at a distance apart from each other, yet there is an inter-relationship between them which constitutes such a combination that the identity of a system is not to be overlooked. In other words, the power unit is functionless unless united with the hand implement, and vice versa, the bond between the two being a column of liquid which is maintained in absolute solidarity lboth by fairly heavy springs at the closure terminals of the column and by a static pressure device that branches of! from one side of the column with which it is in communication. y

Referring first to the details of the power unit I, it is observed in Fig. 1 that an electric motor 4 is employed as the prime mover. This motor may be of any desired horse power because the greater the rating of the motor the heavier will be the character of work capable of being done. For illustration, an ordinary half horse power motor has been demonstratedas being capable of driving heavy spikes through heavy timbers, driving holes through concrete and doing similar heavy work.

vThis motor ls secured at 5 to the cross members 8 which are herein regarded as being parts of a frame 1. This frame is suitably secured to a base 8. The manner in which the motor 4 is mounted, and the manner of assemblage of the components of the power unit I, are of little im` l portance.

The driving shaft 9 of the motor (Fig. 4) is coupled at III in any desired way to the cam shaft II of the impulse member I2. This shaft is shown to have a single cam I3 amxed to it (Fig.

5) but in practice the cam I3 may have two lobes II. These bushings are fitted tightly in bores -I6 whichv occur partly in the body I1 of the impulse member I2 and partly in the cap I8 thereof. The latter is secured by bolts I9 which if i1; be so desired, could be .substituted by studs fixedly driven in the body I1, projectible through openings in the cap I8 and threaded to receive securing nuts.

In eitherevent the bushings I5 are clamped iirmly in position so as not to turn, and in order to avoid the possibility of any liquid leakage a packing 20 and gland 2l are added; as shown. A

packing provision such as this is not needed at the leftend of the shaft II because-this'is con- Lfrontedby-.vthe closure wall of the body I1 and capI8. A

' flanged at I1a (Fig. 1). Therev is one of these flanges on .opposite sides of the.

' The body I.1 is

body. and they restvupon the matching channels Y ofthe frame 1. Bolts and nuts I1b are used to secure thev flanges to the channels, and the latter A' chamber 22 provides the operating-space for the cam I3. This chamber appears as a bore 23- spective shoulders. A cylindrical head 28 is slidably mounted in the bore of the bushing 28.

This headis made cylindrical largely for convenience in manufacture.- It is possible to make it cross sectionally non-circular, but to do so involves a somewhat greater cost.

The head 23 is forked at 29. A roller 39 is iournaled between the forks. Said roller may either turn on the axle 3|, in which event the ends of the axle would be iixed in the fork, or the roller may be made rigid with the axle in which event the ends of the latter would turn in the n fork.

rt is to be observed that the crest az of the fork 29 extends vabove the periphery of the roller 39 (Fig. 5). This'makes the cam I3 ride inside of.

of the bearing of the fork crests against the sidel -walls of the cam I3.

A tappet 33 constitutes the important support of the head 28 (F18. 4). This tappet is nothing more than a threaded shank 34 with an exposed head on which the cylinder head rides. A .1am nut 35 is added to lock the adjustments of the tappet in respect to a plunger 36 which carries it. T'he tappet.ad;|ustment is initially necessary to establish a minute but proper clearance between the peripheries of the cam I3 and roller 30 and to maintain that clearance when wear occurs after long use of the tool.

A washer 31 is interposed between the jam nut 35 and the adjacent end of the plunger 3B. This washer provides an abutment for one end of a spring 39, the other end of which bears on the ange of the bushing 21. It is in the bore of the latter that the plunger 436 is slidably mounted. This plunger is part of a piston 39, herein known as the impact piston because it delivers the blows Y These rings ride the internalwall of a bushing 44 which constitutes a cylinder for the piston. 'I'his 1 bushing is tted tightly in the counterbore 45 of a threaded bore 46 introduced into the body I1 from the end opposite yto that from which the previously mentioned bore 23 and counterbores 24, 25 are driven.

A nipple 41 is screwed-into the bore 46. It serves lto keep the bushing 44 in place, although the tight driving of the latter would adequately accomplish that purpose. It is observed in Fig. 4

' that the liquid column I4 extendsthrough the i are made tall enough so that parts emerging from the bottom of the body I 1 will clear the base 8.

nipple 41 up to the impact piston 39. As thecam I3 rotates'with the shaft II the successive im'- uid is virtuallyincompressible, it follows that the impacts are' delivered thereby with no perceptible diminution.

. While on the subject of the impulse member I2, it is Aobserved in Fig. 4 that the liquid column is supplemented with a bleeder 48. 'I'his consists of a manually turnable needle valve 49 which is adapted to engage aY seat 50 for closure. A iateral openingl in thecas'ing 52 of said valve .provides for the escape of entrapped air from the liquid column I4, through a duct 53 that communicates'with the interior of the cylinder 4 4.

lAnelbow 54y (Fig. 4) is screwed into the nipple -adJus'tablj/f carries a screw 6I. v stitutes 'the abutment for a fairly heavy washer 81. A coupling lI6 (Fig. i) Joins the elbow to a short'iitting (Fiss. 1 and '1). This fitting is screwed into.a'.1"6l1. -A'similar tting 58; is screwed into this 1' and one end of the-previously e mentioned hose 8 issecured to this 'fitting by a clamp I9 Aof any desired type. A third fitting 90 is screwed into the I" B1 and it is .this fitting which carries the recoil chamber 6|.

' -As shqwn in Fim?, the recoil chamber 6| consists of 'a cylinder 92 -into the reduced end of which-,the fitting 60 is screwed. j The other end of this cylinder has a threaded closurel 63 which 86 against-which one end of a spring 86 bears.

At this point it isv desired to state that instead of making the recoil chamber 6| separate from the body 1 as herein disclosed, it is quitefeasible to incorporate it within the body. f It is thought unnecessary to illustrate this modlcation because a-bore in the body y|1 (Fig. 4) equivalent to the internal diameter of the cylinder 62, is readily visualized. The-chief advantage in incorporating the recoil chamber in the body |1 lies in manufacture, but the arrangement in Fig. l will be employed quite commonly.

The other end of the spring 96 presses against a piston 61 which, like the piston 39, has a cupV leather 68, and at least one ring 99. It is plainly seen -in Figs. 1 and' 7 that the liquid column Il 'Ihisy 'screw conextends into the recoil chamber 6|, the chamber f 62 of .the'latter constituting a lateral branch of the liquid column. 4

The lspring 66 is quite heavy and does not yield under ordinary circumstances. But if by chance there should be a jamming of the hammer later described, so that the back pressure in the liquid column might tend to burst some of the parts,

thev spring 66 will yield under the excess pressure and thus act as a safety device. On .the same principle the recoil chamber is made to serve as a governor. The pressure of the spring 66 upon the piston 61 and so upon the lateral branch of the liquid column I4, can be diminished by unscrewing the screw 64.

. The result of this unscrewing is to provide a lateral outlet, so to speak, for the power impacts delivered to the column Hl. This, in turn, lessens the force of the impact delivered to the hammer. Conversely, the intensity of the power impacts upon the liquid column can be increased by turning the screw down. The screwy adjustment thus serves the pur-pose of regulating the static pressure upon the liquid column, and as has been brought out before, it is not material where the static pressure device is located in reference to the conduit nor, in fact, is it material that the specic form in Fig. '1 be adhered to.

,The intended purpose is served by requiring the l member 6| to function as a static pressure devdesignated 10 (Figs. 2 and 3). This hammer comprises the piston 1|, hammer shank 12, and hammer head 13. These three parts can be assembled in any desired way; they may be integral if preferred. The shank 12 is of less diameter more rings 11.

than'the piston 1|. This provides a shoulder 1I (Fig. 3) against which the spring abutment washer 15 ia rested.` The piston -1| has a cup leather 18 at its working end'and it has one or A long tube 18 (Fig. 2) provides both the cylinder for the piston 1| land the Iplaceoi! connection of the other end. o! the hose 3. Said connection is made by a clamp 18 or some equivalent.

' A coupling 80 connects a spring tube 8| at one oi' its'ends to the long tube 18. A reducer '82 on the other end of the spring tube 8| provides a bearing for the hammer shank 12'. The reducer is shouldered at88' to serve as an abutment for that end of the spring 8.4 opposite to the one which bears against the abutment washer 16. Said reducer has a. peripheral flange 82a which bears on the lwall of the hammer casing and provides a guide. The spring is'housed by the tube 8| hence the name spring tube.

'I'he hammer casing 86 contains most of the parts oi the implement 2. 'Ihe hammer 10 and the tubel 18 which carries it is in floating re.

lationship to the hammer casing. Said casing has a closure 86 at one end. 'I'his closure has a bore 81 in which the tube 18 is capable of reciprocation. Said closure also constitutes the common abutment for the inner end of a pair of springs 88, 89 on the tube 18. Set collars 90, 9| on said tube provide bearings for the remote l ends of said springs. These springs are equalizers. They serve to maintain the tube 18 and its immediately carried parts in what might be called a normalposition in reference to the hammer casing 85. Said springs are also shock absorbers because without them it would be virtually impossible to wield the implement 2 with the power unit I in operation. The wielding is done through a handle 92. The operator grasps this and directs the implement 2 wheresoevery he will.

An extension l93 of the casing 85 carries what is generally designated an anvil 94. The extension is removably attached at 95 to the casing 95, the purpose of detachment being to provide access to the inner end of the anvil.

A further purpose of the movable attachment of the extension 93 at 95, which attachment comn prises the screw threads shown, is to enable the adjustment of the extension in respect to the casing and thereby to regulate the position of the anvil 94 in relationship to the hammer head 13. It is entirely practicable to make the screw threads at 95 tight enough to insure the maintenance of the extension 93 in the adjusted position. If the screw threads cannot be relied upon for this function then it is regarded as an obvious expedient to employ some known clamping device that will fix the extension when adjusted.

The latter comprises a stem 96 which is slidable in the bore 91 of a partition 98. The latter is secured in the extension 93 in any desired way, for example by spot welding.' Strikers 99, |00 are attached to the respective ends of the stem 96. 'Ihe first of these is guided in the bore |0| of a cap |02 at which the tip of the striker 99 is exposed. The otherstriker |00 is in normally spaced relationship to the head 13, but the space is taken up by the natural downward pressure of the implement against the work when the handle 92 is grasped.

Springs |03, |04 bear against the strikers 99, |00 at their remote ends and bear commonly against the partition 98. These springs serve to keep the anvil 94 in a normal position in the end of the casing 88, and yield only Vwhen the hammer head 13 is brought to bear against the anvil in the manner previously stated.

The operation is readily understood. The motor 4 is connectible with a source of electric current usually being controlled by a switch (not shown). The revolution of the drive shaft 9 (Fig. 4) actuates the cam I3 so that impacts are delivered to the cylinder head 28 in rapid succession. 'I'he number of impacts will be at least one for every revolution of the drive shaft. As previously pointed out the number of impacts can be multiplied by using plural cams.

The spring 38 (Fig. 4) tends to keep the piston 39 in its outward position in the liquid conduit.

As each impact is delivered to the cylinder head 28 the spring 38 yields, permitting the. impact to be transferred to the liquid column I4. By tracing this column from Fig. 4 to Fig. 2 by way of the hose 3, it is seen that each impact is delivered to the piston 1I of the hammer 18. The operator supposedly has the implement 2 in his hand. The anvil 94 is rested against the work. The spring |83 yields, thereby permitting the engagement of the striker |88 withthe hammer head 13..

The impacts against the piston 1I of the hamvmer 18 are delivered to the work through the mary purpose of keeping the pressure of the liquid column uniform. Any tendency toward nuctuation in the latter is smoothed out by the reanvil 94. There will be some vibration of the long tube 18. The amplitude of vibration will, however, be less than that of the hammer 18, This fact is due to the inertia .of the tube 18. 'Ihe extension, of the hammer 18 by force of a blow will, naturally, partially compress the spring 84. The resultant motion is transferred to the tube 18. But the latter, due to the inertia mentioned, exhibits a tendency to lag under the impetus of the motion of the spring 84, thus permitting a pronounced outer motion of the hammer upon the application of the -rst hydraulic impact.

When this action is multiplied with extreme rapidity the result is a free vibration of the hammer 18, but a retarded vibration of the tube 18. There will also be some vibration of other parts of the conduit, for example, the hose 3. But this is not objectionable, and the fact that vibration occurs in the conduit does not diminish the eiectiveness of the hammer 18 in the least. Nor does the vibration which is transmitted to the hammer casing 85 through the instrumentality of the springs 88, 89, disturb the operator. These springs absorb much of the shock due to the diminished vibration of the tube 18.

There is another factor which it is desired to bring out. According to the present showing the inside diameter of the liquid conduit is the same from beginning to end. That is to say, the inside diameter of the tube 18 (Fig. 2) is the samev and hammer piston 1I it is in turn possible tol vary the power impacts and length of strokes. For example, an increase in the inside diameter of the cylinder 44 will produce a much harder power impact against the hammer 18 than when the conduit is of the previously mentioned uni'- form size.

The recoil chamber 6Iv (Fig. "1)l has the prisiliently backed piston 81. The recoil chamber is also capable of producing changes in the force of the blows of the hammer -18 because by backing of! the screws 84 the pressure on the liquid column will be lessened and this in turn will produce somev dispersion of the power impacts delivered in the impulse member I2.

In conclusion it is desired to point out that the earlier reference to the electric motor 4 (Fig. 1) is not to be regarded as a limitation on the prime mover capable of employment. This motor may be substituted by a gasoline engine, in fact by any type of motor capable of turning the shaft 8 at a high rate. v Y

Further reference is desired to be made to the hand implement 2. This too is not to be considered as a limitation for this reason; it is conceivable that the power impulses delivered to the hydraulic column I4 are not` necessarily terminated at the hammer of a manually wieldable implement. The latter can be set in a perfectly rigid position.

In such an event the casing 85 is not necessarily used. I'he tube 18 of the hammer and tube assemblage 18, 18, would then be held stationary and the vibrations of the hammer head 13 would be applied to the work with virtual disregard as to what its nature might be. For instance, the reciprocable hammer might be the reciprocable element of a jig saw 'or it may be applied to some other type of power tool.

We claim:

l. An impact implement consisting of a casing. a tube slidable in said casing and constituting one terminal .of a hydraulic column, a hammer reciprocable in said tube and abutting the hydraulic column, an anvil in Vspring-floated relationship to the hammer, means guiding the tube and hammer assemblage in the casing and in re spect to said anvil, and shock absorber means abutting portions of both the casing and tube, floating the tube and hammer assemblage in said sliding relationship.

2. An impact implement consisting of a casing having an abutment at one end, a tube constitutlng one terminal of a hydraulic column, said tube partly occupying the casing and being slidable in said abutment, a piston structure reciprocable in the inner end of the tube and having a shoulder. a spring exerting pressure at one end against said shoulder, means containing the spring, providing an abutment for the other end 3. An impact implement consisting of a casing having an abutment at one end, a tube constituting one terminal of a hydraulic column, said tube partly occupying the casing and being medially slidable in said abutment, collars attached to the tube at the respective sides of the Y abutment, springs carried by the tube commonly resting against the abutment and engaging the respective collars, a piston structure reciprocable in the vinner endofthe tube and havingl a shoulder, a spring exerting pressure at one end against said shoulder, a tube containing the spring and having means vagainst which the lother end oi the spring is rested.and a coupling autres securing the two to'each otherpsaid 'cou-y pling engaging the wall of the casing and havtuuns one .terminal or a. hydraulic column, said tube being slidably guided by the abutment ing a slidable t ther'eaiiist to listin theimby the tube and engaging the abutment on opposite sides, .collars attached to the tube. 'against whichv therespective springs are rested, a piston means and in turn having abutment means out.

standing therefrom, a `pair of springs vin'utually engaging the abutment means of the respective -`casing and tube to sustain thetubein'iioating e relationship to the casing insofar as axial movement is concerned, a piston contained by the tube. confronting the contiguous end of the hy- 'draulic column and therefore being adaptedto receive power impacts delivered through lsaid column, said piston having abutment means, and

reciprocable in the inner end of the tube, a hammer shank extending from the piston andk being of smaller size to denne-.a shoulder, a spring carried by said hammer Ashank exerting pressure at one end againstsaid shoulder, av tube-containing the.spring, and a pair of coupling members l secured to the spring tube, one of said members connecting the two tubes together, the othf er providing an abutment iorthe last-named spring, both couplings engaging the wail of the casing to provide a slidable support. v

.5. An impact implement consisting of a casing having an abutment at one end and a partition at the other end, a tube constituting one terminal of a hydraulic column. said tube partly occupying the casing and being vslidable in said abutment, resilient means mutually inter-engaged with the tube and said abutment for equalizing the tub in respect to the casing, a piston and hammer structure reciprocable in the inner end of the tube, a spring exerting pressure against said structure, tending to resist` impacts delivered to such structure, means carried by the tube in turn carrying said spring so that the reactions of said spring are delivered to the tube, and an anvil slidably carried by the partition, being in Vstriking position in' reference to the piston and hammer structure.

6. An impact implement consisting of a casing having an abutment at one end' and a partition at the other end, a tube constituting one terminal of a hydraulic column, said tube partly occupying the casing and being slidable in lsaid abutment, resilientmeans mutually interengaged with the tube and said abutment for equalizing the tube in respect to the casing, a piston and hammer structure reciprocable inthe inner end of the tube, a spring exerting pressure against said structure, tending to resist impacts delivered to such structure, means carried by the tube in turn carrying said spring so that the reactions of said spring are delivered to the tube, an anvil slidably carried by the partition, being in striking position in reference to the piston and hammer structure, and an equalizer spring carried by the anvil, being situated on opposite sides of the partition, said spring engaging both the partition and portions of the anvil serving to keep the anvil in a normal position.

7. An impact implement consisting of a casan expansion spring pushing against a part off. the tube and against the abutment on the Piston thereby to tend to drive the piston against the hydraulic column. i

9. An impact implement consisting of a casing, aAtube in the casing, opposed resilient means commonly abutted against a portion 'of the casing and against spacedportions of the tube providing a floating relationship of the tube to the casing, said tube being adapted to be supplied from one end-'with a percussive iiuid, and a hammer reciprocably fitted in the other end of said tube.

10. ',An impact implement consisting of a casin'g having an abutment at'one end, a tube slidalbie in said abutment, carrying springsvengaging opposite sides of the abutment and maintaining a floating relationship of the tube to the casing, and a hammer reciprocable in one end of said tube in response to iiuid impacts in said tube.

11. In combination a conduit, said conduit containingl a liquid column, a movable closure for each end of` the conduit in direct contact with the ends of' the column, a spring backing the closure at one end of the column', means for imparting strokesto the closure at the other end of the column for delivery through thecolumn -to the spring-backed closure, a static pressure device branching oli from said conduit at a point beyond the farthest inward movement .of the inner end of either closure, thus a'iording communication of the column with said device and the integrity of a head of said liquid from the column, `said device embodying a piston in direct and sole superimposition upon said head, and means acting on said piston for maintaining said liquid column at a pressure suillcientto give the liquid column a frequency exceeding that of the strokes imparted by said stroke-imparting means, thereby to insure the rigidity of the column and its immunity to a wave action.

l2. In combination a conduit, a blow-receiving closure in one end of the conduit, aworkproducing closure in the other end of the conduit, a spring backing the second closure, said conduit and closures coniining a rigid reciprocable column of liquid with the inner ends of the closures being in direct contact with the ends of the reciprocable column, pressure head means in permanent .and uninterrupted communication ing having an abutment at one end, a tube conof the piston structure, said means engaging the wall of the casing to provide a slidable support.

8. An impact implementconsisting of a casing having internal abutment means, atube consti-4 with the conduit and maintaining the column of liquid-under a. perpetual pressure for not only definitely fixing the column and closures as a solid mass-unit capable of instantaneous reciprocation and for maintaining said column of liq' uid and closures as an integral formation but for partially compressing the spring, and means imparting strokes to the blow-receiving closure for reciprocating the column and closures as an integral formation in one direction While simultaneously further compressing thev spring, said spring returning the integral formation 'between the strokes of said stroke-imparting means.

13. In combination, a conduit, a blow-receiving closure in one end of the conduit, a work'- producing closure in the. other end of the conduit, a spring backing the second closure. said Aclosures being in direct contact with the ends of,

the reciprocable column, means placing-the column of liquid under a constant pressure for not only definitely nxing the column and closures as a solid mass-unit capable of instantaneous reciprocation and for maintaining said column of liquid and closures as an integral formation but for partially compressing the spring, and means imparting strokes to the blow-receiving closure for reciprocating the column and closures as an integral formation in one direction while simultaneously further compressing the spring, said spring returning the integral formation `between 14. A hydraulic power transmission device comprising a conduit, said conduit containing a liquid column, a movable closure for each end of the conduit indirect contact with the ends of the liquid column, a spring backing the closure'at one end of the column, means for imparting strokes to the closure at the other end of the column for delivery through the column to the springbacked closure, a iixed pressurev device branching oil! from and in communication with said conduit thus establishing communication of the column with said device, and means within said device bearing down on the liquid column for maintaining said column at a fixed-pressure suillcient to give the liquid column a frequency exceeding that of the strokes imparted by said stroke-imparting means, thereby to insure the rigidity of the column and its immunity to wave action.

at said cylinder, said-conduit` being flexible in nature and extending off from said implement to a point of remote termination of its other end, a reciprocable force-receiving closure in said other end of the conduit. said conduit together with the piston in said one end and the closure in the other end confining a rigid reciprocable column of liquid in direct and perpetual contact with the inner ends of said piston and closure, pressure means in communication with the column' placing the column under a predetermined pressure and volume for a4 given operation for not ronly maintaining and regulating the rigidity of said column together with said pisthn and closure as a solid mass-unit formation capable of instantaneous reciprocation, but also for initially and partially compressing and energizing the resilient return means to establish a preliminary and constant loading of the return means thereby maintaining a predetermined length of stroke of the piston and regulating the pressure on said return means andthe position of the piston with reference to said resilient return means, and means for imparting rapid periodicr strokes t0 .said closure for moving said mass-unit formation in one direction vwhile simultaneously further compressing and energizing the resilient return means, said return means rapidly returning the mass-unit formation between the strokes of said force-imparting means.

CHARLES F. WARREN. WILLIAM R. SMITH.

resilient return 

